1. Field of the Invention
This patent relates to manually operated electrical switching systems. More particularly, this patent relates to a system for switching a selected group of household circuits from utility company service to a standby generator using a single manual switch.
2. Description of the Related Art
Typically, local electric utility companies supply the alternating current for household electrical power. If the utility supplied electrical power is somehow interrupted, a portable generator system can be used to temporarily maintain electrical power needed for critical systems, such as heating, refrigeration, hot water and lighting. Typically, this type of system is used for a household, but the same system could be used in commercial, industrial, municipal and farm applications. For the sake of simplicity and clarity, these additional applications are included in all situations referred to hereafter as xe2x80x9chouseholdxe2x80x9d.
The portable generator usually is placed outside the building and is connected to a generator transfer panel located inside the building. This connection can be made via an exterior mounted power inlet box or via a direct connection to the generator transfer panel. The generator transfer panel is connected via an electrical conduit or cable to the main electrical panel or load center. The generator transfer panel is typically mounted adjacent to the main electric panel. Inside the generator transfer panel is the transfer switching mechanism (and other components as outlined below) that directs the flow of electricity from either the utility company or the generator to selected electrical circuits in the building.
Because generator capacity is usually less than the building""s total electrical demand, it is usually desirable to limit the number of circuits running on the generator. This is accomplished with the aid of the transfer switching mechanism inside the generator transfer panel. Conventional transfer switching mechanisms typically employ eight to ten double pole rocker type switches (a.k.a. double pole/double throw switches) to control the path of electricity from the generator to the load center.
A disadvantage of such conventional transfer switching mechanisms is that they involve a complicated system of multiple switches and circuit breakers that can lead to mistakes in transferring electrical power to the desired circuits. Also, conventional transfer switches do not have positive break contacts and so can lead to accidental back feed into the generator from the utility or into the utility from the generator. If a feedback situation occurs, a short circuit can develop causing a fire or explosion. Also, conventional transfer switches require more than one power feed from the generator, which increases complexity and can lead to wiring errors during installation.
Thus it is an object of the present invention to provide a simple system to transfer electrical power from utility company service to a standby generator.
A further object of the present invention is to provide a system for switching a group of circuits from among a number of groups of pre-selected circuits from utility company service to standby generator service using a single multi-position switch.
A still further object of the present invention is to provide a switching system that prevents the possibility of back feed either from the generator to the utility or from the utility to the generator.
A still further object of the present invention is to provide a generator transfer switching system that provides a common generator feed with a single switch to all selected household circuits.
Yet another object of the present invention is to provide a switching system that uses a conventional cam-type switch to transfer generator power to a selected group of household circuits.
Still another object of the present invention is to provide a generator transfer system that can be readily expanded or reduced to switch the appropriate number of household circuits.
Still another object of the present invention is to provide a generator transfer system that provides a means of installing either fuses or circuit breakers to provide short circuit protection for individual household circuits.
The present invention is a generator transfer switching system that enables a user to select, using a multi-position generator transfer switch, which household circuits to transfer over to generator service. The system comprises an electrical generator, a multi-position generator transfer switch and a main electrical panel. The multi-position generator transfer switch is electrically interposed between the electrical generator and the main electric panel.
The multi-position generator transfer switch comprises a contact block having multiple stages, each stage containing electrical contacts and operable cams connected to the contacts. The cams are mounted on a shaft running through the center of the block and connected at one end to a handle. The handle can be manually turned to select which household circuits are to be converted from utility company service to electric generator service.